In recent years, a type of mobile communications network known as an “ad-hoc” network has been developed. In this type of network, each mobile node is capable of operating as a base station or router for the other mobile nodes, thus eliminating the need for a fixed infrastructure of base stations. As can be appreciated by one skilled in the art, network nodes transmit and receive data packet communications in a multiplexed format, such as time-division multiple access (TDMA) format, code-division multiple access (CDMA) format, or frequency-division multiple access (FDMA) format.
More sophisticated ad-hoc networks are also being developed which, in addition to enabling mobile nodes to communicate with each other as in a conventional ad-hoc network, further enable the mobile nodes to access a fixed network and thus communicate with other mobile nodes, such as those on the public switched telephone network (PSTN), and on other networks such as the Internet. Details of these advanced types of ad-hoc networks are described in U.S. Pat. No. 7,072,650 entitled “Ad Hoc Peer-to-Peer Mobile Radio Access System Interfaced to the PSTN and Cellular Networks”, granted on Jul. 4, 2006, in U.S. Pat. No. 6,807,165 entitled “Time Division Protocol for an Ad-Hoc, Peer-to-Peer Radio Network Having Coordinating Channel Access to Shared Parallel Data Channels with Separate Reservation Channel”, granted Oct. 19, 2004, and in U.S. Pat. No. 6,873,839 entitled “Prioritized-Routing for an Ad-Hoc, Peer-to-Peer, Mobile Radio Access System”, granted Mar. 29, 2005, the entire content of each being incorporated herein by reference.
As can be appreciated by one skilled in the art, certain nodes in multihopping wireless networks may receive more traffic than others, and therefore become congested. Accordingly, it is desirable to attempt to avoid congested nodes when routing packets in the network. A publication by C. Y. Wan, S. B. Eisenman, and A. T. Campbell entitled “CODA: Congestion Detection and Avoidance in Sensor Networks”, SenSys 2003, describes a congestion control algorithm for networks. In accordance with this algorithm, a suppression message for reducing traffic is broadcasted by devices in the network. However, the reliability of receiving this message is based on the channel quality and can require broadcasting of the message multiple times during the congested period. Hence, although these messages are propagated upstream through the network toward the sources of the traffic, these messages may not always be received by the sources. Furthermore, a node that receives the suppression message may choose to not propagate the message if its local network conditions are acceptable. Therefore, this technique for attempting to avoid congestion is not reliable.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.